As far as I can see, it would involve changing the values of a whole bunch of resistors, but exactly which ones, and to what values, is beyond my capabilities to figure out.
I looked at the schem for his other svf to find clues, but they are quite different designs.

Any clues?

CLast edited by Coriolis on Tue Jan 16, 2007 12:10 pm; edited 1 time in total

Sorry to dig up this old thread, but I was just looking at the schems for both of Ray's svf designs and wondered:

On his vc res design, which he sells boards for, the frequency pot sits between + and - 12V, with the wiper carrying the cv.

On the other one (the one I'm building), frequency pot sits between + 12v and ground, with the wiper carrying the cv!

What's going on there? I know I said in the first post of this thread, that they were two "very different" designs, but I take that back: apart from the vc res part, they actually look very much the same, except for this frequency pot business. Could this be why running it on +/-15V screws things up?

Well, it's official - I'm a grade-A moron.
I think I've been over that board a dozen times or so, checking for component values, solder bridges, etc. For some reason though, I didn't think to check the trimmer - how about that, instead of a 100R trimmer, I put in a 100K!

Now it works...
Guess there's a lesson in there: To debug a circuit effectively, assume that you have done everything wrong!

Only thing that isn't quite there yet, is that it doesn't self-oscillate at max resonance - which it is supposed to do. Am I right in thinking about reducing the value of R4 (47k at point "Q1" next to the input) to get more feedback?

To accept that there may be a fault in your beautiful new creation, and then go and find said fault, accept it, and own it, and fix it! Now that's the work of genius!_________________What makes a space ours, is what we put there, and what we do there.

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